Ch. 18 Hemodynamics Flashcards
__________________________________ is the study of blood moving through the circulatory system.
Hemodynamics is the study of blood moving through the circulatory system
______________, also called volume flow rate, indicates the volume of blood moving during a particular time.
Flow, also called flow rate, indicates the volume of blood moving during a particular time.
Units for flow:
volume/ time
_______________________ indicates the speed or swiftness of a fluid moving from one location to another.
Velocity indicates the speed or swiftness of a fluid moving from one location to another
Units for velocity:
distance/ time
what are the 3 basic forms of bloodflow?
- pulsatile
- phasic
- steady
________________________ flow is when blood accelerates and decelerates as a result of cardiac contraction; therefore this flow appears in the arterial circulation.
Pulsatile flow is when blood accelerates and decelerates as a result of cardiac contraction; therefore this flow appears in the arterial circulation
________________________ flow also occurs when blood accelerates and decelerates as a result of respiration; appears in the venous circulation.
Phasic flow also occurs when blood accelerates and decelerates as a result of respiration; appears in the venous circulation
______________________ flow occurs when a fluid moves at a constant speed or velocity.
Steady flow occurs when a fluid moves at a constant speed or velocity.
____________________ flow is when the flow streamlines are aligned and parallel (normal physiologic states)
Laminar flow is when the flow streamlines are aligned and parallel (normal physiologic states)
What are the 2 forms of Laminar flow?
- Plug Flow
- Parabolic Flow
_______________ flow occurs when all of the layers and blood cells travel at the same velocity.
Plug flow occurs when all of the layers and blood cells travel at the same velocity.
________________ flow has a bullet-shaped profile. Velocity is highest in the center of the lumen, and gradually decreases to its minimum at the vessel wall.
Parabolic flow has a bullet-shaped profile. Velocity is highest in the center of the lumen, and gradually decreases to its minimum at the vessel wall.
The _____________________________ predicts whether flow is laminar or turbulent.
The Reynolds number predicts whether flow is laminar or turbulent
The Reynolds number for laminar flow is less than _________________
The Reynolds number for laminar flow is less than 1,500
____________________ flow is characterized by chaotic flow patterns in many different directions and at many speeds.
Turbulent flow is characterized by chaotic flow patterns in many different directions and at many speeds
Turbulence is often associated with cardiovascular ______________________ and elevated blood ______________________
Turbulence is often associated with cardiovascular pathology and elevated blood velocities
sound associated with turbulence is called a _________________ or _____________________
sound associated with turbulence is called a murmur or bruit
Tissue vibration associated with turbulence is called a _____________
Tissue vibration associated with turbulence is called a thrill
The Reynolds number for turbulent flow is greater than ________________
The Reynolds number for turbulent flow is greater than 2,000
When blood moves from regions of higher energy to lower energy this is called __________________________ (pressure difference)
When blood moves from regions of higher energy to lower energy this is called energy gradient (pressure difference)
What are the 3 energy forms associated with blood?
- kinetic energy
- pressure or potential energy
- gravitational energy
_______________________ energy is the ability of blood to do work as a result of its velocity. Associated with a moving object
Kinetic energy is the ability of blood to do work as a result of its velocity
Kinetic energy is determined by two factors:
an objects _______________ and the ______________ at which it moves
Kinectic energy is determined by
an objects mass and the speed at which it moves
____________________ or ________________________ energy is pressure force energy, it is the main form of energy found in flowing blood
Pressure Energy or Potential Energy is pressure force energy, it is the main form of energy found in flowing blood_____
How does pressure create blood flow?
by overcoming resistance
_________________________ energy is the ability to do work as a result of gravity, it is a form of stored or potential energy.
Gravitational Energy is the ability to do work as a result of gravity, it is a form of stored or potential energy
As blood flows through the circulation, energy is lost in 3 ways:
- viscous loss
- friction loss
- inertial loss
_______________________describes the thickness of a fluid; so __________________ energy loss is associated with blood overcoming its internal stickiness.
Viscosity describes the thickness of a fluid; so viscous energy loss is associated with blood overcoming its internal stickiness
Viscous energy loss in blood is determined by ___________________________
Viscous energy loss in blood is determined by hematocrit
What is the normal average hematocrit?
45%
_________________________ energy loss occurs when flow energy is converted to heat as one object rubs against another.
Frictional energy loss occurs when flow energy is converted to heat as one object rubs against another
____________________ energy loss is the tendency of blood to resist changes in velocity
Inertial energy loss is the tendency of blood to resist changes in velocity
When does Inertial energy loss occur?
- pulsatile flow
- phasic flow
- velocity changes at a stenosis
Velocity is ___________________ when the vessel narrows, and ___________________ when the vessel widens
Velocity is greater when the vessel narrows, and weaker when the vessel widens
______________________is the narrowing in the lumen of a vessel
stenosis is the narrowing in the lumen of a vessel
What are the effects of a stenosis?
change in flow direction
increased velocity as vessel narrows
tubulence downstream form the stenosis
pressure gradient across the stenosis
loss of pulsatility
__________________________________ states that generally as a vessel narrows flow velocity increases and pressure simultaneously decreases. Pressure energy is converted into kinetic energy.
Bernoulli’s Principle states that generally as a vessel narrows flow velocity increases and pressure simultaneously decreases. Pressure energy is converted into kinetic energy.
pressure gradient =
flow x resistance
voltage =
current x resistance
How does Ohms law relate to pressure gradient?
pressure gradient is analogous to voltage; flow is analogous to current; resistance is the same
Electrical resistance is reported in units of:
Ohms
What are the circulatory system’s resistance vessels?
arterioles
What are the main characteristics of veins?
Thin-walled and collapsible, low resistance vessels
Describe veins during normal function
low pressure, partially filled with blood, partially expanded (flattened hourglass shape)
Venous inflow
hourglass cross sectional shape changes to oval then to round. This allows veins to accommodate a large volume increase with a very small increase in pressure. Once veins empty out they return to their original hourglass shape
Why do veins expand during inflow?
This allows a high volume of blood with only a small pressure increase; resistance decreases and outflow to heart increases
_____________________________________ is pressure related to the weight of blood pressing on a vessel measured at a height above or below heart level.
Hydrostatic Pressure is pressure related to the weight of blood pressing on a vessel measured at a height above or below heart level.
When supine, hydrostatic pressure is
zero everywhere
below the heart the hydrostatic pressure is
positive, resulting in a measurement that is too high
above the heart, hydrostatic pressure is
negative, resulting in a measurement that is too low
At the heart, the hydrostatic pressure is
zero, the move accurate measurement
How does respiration have an effect on the venous system?
- the venous system is low pressure
- muscles responsible for respiration alter pressures in the thorax and abdomen
What 2 venous flows does breathing affect?
- venous flow in the legs
- venous return to the heart which compromises venous flow from the head, arms, and IVC to the heart
With Inspiration:
Diaphragm moves _______________________ toward the abdomen
Thoracic pressure _________________________
Abdominal pressure ____________________________
Venous return to the heart ________________________
Venous flow in legs ___________________________
With Inspiration:
Diaphragm moves downward toward the abdomen
Thoracic pressure decreases
Abdominal pressure increases
Venous return to the heart increases
Venous flow in the legs decreases
With Expiration:
Diaphragm moves _________________________ into the thorax
Thoracic pressure _________________________
Abdominal pressure __________________________
Venous return to the heart ______________________
Venous flow in legs ________________________
With Expiration:
Diaphragm moves upward into the thorax
Thoracic pressure increases
Abdominal pressure decreases
Venous return to the heart decreases
Venous flow in the legs increases
